Paper pulp and paper



Patented Aug. 31, 1926.

UNHTE srras mama IBERTR-AND S. SUMMERS, OF PORT HURON, MICHIGAN."

PAPER PULP AND PAPER.

4N0 Drawing.

My invention has for its object the improvement of the quality of the pulp andpaper made thereof. It is based on the discovery which I have made that if the paper 5 making materials are treated with phosphoric acid or soluble salts thereof in the course of their preparation the phosphoric acid combines or is incorporated with the cellulose in such a way that even after bleaching the material will show a firm test for phosphoric acid. The presence of phosphoric acid in the pulp gives the paper formed therefrom a certain toughness and characteristic feel, aids its bleaching and facilitates the hydration of the pulp when treated in the beater.

The combination may be brought about in several Ways and in its broader aspect the invention is independent of the particular manner by which this combination or assimilation of the phosphoric acid with the cellulose is effected. Thus the phosphoric acid may be introduced into the digester with the material to be pulped. It may be 2 introduced into the beating engine with the pulp when the latter is being beaten. Or, the phosphoric acid may be used to dissolve material like casein, size, etc., and the resulting solution introduced into the beating engine or used to coat the paper.

The invention is particularly applicable to pulps made from the kraft process wherein I the combination of the cellulose of the kraft pulp with the phosphoric acid also aids the bleaching to such an extent as to make it possible to produce a white pulp of high color and at the same time very soft and strong.

I prefer to use the phosphoric acid in the form of one of its soluble salts, and trisodium-phosphat-e has been found to be satisfactory for the purpose.

The phosphoric acid addition is found to be of advantage in the digesting process whether graft liquor or the usual sulphite digesting liquor be employed. The addition of the phosphoric acid to kraft liquor has the unexpected and very desirable feature of preventing the very disagreeable odors characteristic of the kraft process. The

Application filed. July 9,

1924. Serial No. 724,972.

paper and paper pulp resulting from the process where phosphoric acid is added, whatever the nature of the digesting liquor employed, evidences the presence of phosphoric acid as above stated.

In the beating operation the action of hydration, which is achieved or assisted by the use of phosphoric acid, may be carried to any desired extent. If a less degree of hydration is effected it will be found that 0 the resultant sheet will have a noticeable effect of sizing, and if the hydration is carried further the sizing effect is more pronounced. A more complete hydration gives the characteristics of imitation parchment and grease-proof papers, depending to some extent upon the nature of the stock treated. In any case, the paper pulp or sheet is found to contain an appreciable amount of phosphoric acid which is largely responsible for the characteristics described. The use of the phosphoric acid does not preclude the additions of such other materials as are commonly employed in the paper of the kind referred to, such as starch, casein, silicate of soda, etc. The eifect of the phosphoric acid is added to that of the additions referred to. I have found the addition of starch to be particularly desirable especially in case a fully grease-proof sheet is desired.

I wlll now describe a typical example of the use of my proved process in which the phosphoric acid is added in the beater: To a body of 1600 pounds of air dried stock contained in a heater, 150 to 300 pounds of phosphate, preferably in the form of tri sodium-phosphate, is added. To the mixture I may add about 150 pounds of starch which has been previously jellified by hot water and to the whole add the usual quantity of water. The roll of the beating engine is then preferably set down hard and the stock beaten until a sample thereof shows the desired degree of hydration. The beater is then dropped and run over the machine in the usual manner. By reason of the hydrating effect of the phosphates if the stock is sufficiently beaten, the resultant sheet will be found to have the effect of having a heavy coat of size. A much smaller amount of phosphate, for example 50 pounds, will give I claim: 10

a noticeable size effect to the finished sheet. 1. As an article of manufacture, hydro Even in acid solution the hydrolizing effect lyzed paper pulp containing an appreciable is evident, but as above stated I prefer to use amount of phosphoric acid compounds.

a decidedly alkaline solution. 2. As an article of manufacture,v hydro- As heretofore stated, the paper and paper lyzed cellulose fibre containing an appreci- 15 pulp produced by my process is or may be able amount of phosphoric acid compounds.

more or less hydrolized and contains an appreciable content of phosphoric acid. BERTRAND S. SUMMERS. 

